Dabour Hub EGEgyptian Curriculum 2026/2027
3-2 (a) The differential and the standard integrals

3-2 (a) The differential and the standard integrals

Point 3 of 12 — Lesson 1: Integration Techniques (Substitution and By Parts) and Definite IntegralsQuestion bank: 5 questions (5 with pictures)

03 3-2 (a) The differential and the standard integrals

The differential

  • If y=f(x) is differentiable, the differential of y is dy=f′(x) dx
  • The differential of x is dx=Δx.
  • It comes from ΔyΔx→f′(x) as Δx→0.
  • For a product of two functions z and ℓ of x: d(zℓ)=z dℓ+ℓ dz.
✍️ Worked examples

Example 5: Find the differential of (a) y=e2x−3 (b) V=43πr3 with respect to r.

Solution:

  • (a) dy=y′ dx=2e2x−3 dx.
  • (b) dV=V′ dr=4πr2 dr.

Standard integrals (reverse of the standard derivatives)

  • ∫xn dx=xn+1n+1+c,  n≠−1.
  • ∫cos⁡x dx=sin⁡x+c and ∫sin⁡x dx=−cos⁡x+c.
  • ∫sec⁡2x dx=tan⁡x+c.
  • ∫ex dx=ex+c and ∫ax dx=axln⁡a+c.
  • ∫1x dx=ln⁡∣x∣+c.

📝 Question bank for this point

5 questions linked to this point only, 5 of them with pictures.